Reba, a calendar year taxpayer, owns an office building that she uses in her business. The building is involuntarily converted on November 15, 2017. On January 5, 2018, Reba receives enough proceeds to produce a realized gain. What is the latest date she can replace the building and qualify for § 1033 postponement treatment if the conversion event is:

a. A flood?

b. A condemnation?

c. A tornado?